Control Strategy of Microgrid Based on Single-Stage PV Microinverters Without Energy Storage

Single-stage microinverters (MIs) are widely used in household photovoltaic (PV) generation, owing to their compact structure, high power density, and high efficiency. However, control for the single-stage MIs is more difficult than two-stage ones due to the limited control freedoms, especially in islanded applications without energy storage units. This paper proposes a novel control strategy for single-stage MIs, which form a microgrid capable of operating in both islanded and grid-connected modes. In islanded operation, MIs are basically operated in grid-forming mode to autonomously share load power based on droop and virtual synchronous generator (VSG) control. If the autonomously allocated power of a single MI exceeds the maximum available power of its PV module, it can automatically switch to grid-following mode without detecting the maximum available power of PV module. Finally, the proposed control strategy is verified based on a microgrid composed of two MIs in simulation and experiment.